Hi

I have the following model :

class Project(models.Model):  
    _inherit = 'project.project'
    releases_ids= fields.Many2many('project_extension.release')
sprint_ids= fields.Many2many('project_extension.sprint')

class Release(models.Model):
    _name = 'project_extension.release'
     project_id = fields.Many2one('project.project', string="Project")

class Sprint(models.Model):
    _name = 'project_extension.sprint'
    project_id = fields.Many2one('project.project')
    release_id = fields.Many2one('project_extension.release')

I want my sprints to be in the same project as there parent release (and the other way), but I don't know the better way to express it.

Should I make it with python constraint, domain filter, computed field (with get and inverse set function) or with a onchange ?

Thanks for your help.